Composite ceramic armor

ABSTRACT

PRESENTLY KNOWN COMPOSITE CERAMIC ARMOR PANELS DESIGNED FOR PROTECTION AGAINST SMALL ARMS FIRE CONSIST OF DENSE CERAMIC PLATES ADHERED TO A BACKING. ACCORDING TO THE PRESENT INVENTION, THE PREFERRED BACKING IS ALUMINUM ALLOY. IN ORDER TO INCREASE THE BEAM STRENGTH OF A FREE EDGE, TO MINIMIZED DEFLECTION UNDER IMPACT AND TO INCREASE THE OVERALL EFFECTIVENESS OF THE ARMOR, THE METAL BACKING PLATE IS FORMED NEAR THE FREE EDGE INTO AN ENCLOSING FLANGE OR LIP WHICH EXTENDS FROM THE BACKING PLATE AT AN ANGLE OF SUBSTANTIALLY 90* ADJOINING THE FACE PLATE AND MATERIALLY STIFFENING AND STRENGTHENING THE FREE EDGE.   D R A W I N G

July 13, 1971 w. HAUCK EI'AL 3,592,942

COMPOSITE- CERAMIC ARMOR Filed May 2, 1968 INVENTORS 2004 WflQuc/r 5 4M051 fl: C 055 L M4 @ZAq ATTORNEYS United States Patent 3,592,942 COMPOSITE CERAMIC ARMOR Eldon W. Hauck, Worcester, and Samuel H. Coes, Northboro, Mass, assignors t0 Norton Company, Worcester,

Mass.

Filed May 2, 1968, Ser. No. 726,121 Int. Cl. B321) ]/04, 17/06 US. Cl. 161-44 4 Claims ABSTRACT OF THE DISCLOSURE Presently known composite ceramic armor panels designed for protection against small arms fire consist of dense ceramic plates adhered to a backing. According to the present invention, the preferred backing is aluminum alloy. In order to increase the beam strength of a free edge, to minimize deflection under impact and to increase the overall effectiveness of the armor, the metal backing plate is formed near the free edge into an enclosing flange or lip which extends from the backing plate at an angle of substantially 90, adjoining the face plate and materially stiffening and strengthening the free edge.

BACKGROUND *OF INVENTION New armor systems for protection against high energy projectiles such as small arms fire have recently been developed. One successful type of such armor consists of a hard, high density ceramic plate backed by a bonded laminate of glass cloth adhered thereto. When such armor is struck on its ceramic face by a projectile of sufficiently high energy, the ceramic plate shatters and fails, as does the projectile, and the energy of the projectile is delivered to the glass cloth backing and dissipated in delamination of the bonded layers of the glass cloth. When this occurs, persons or objects protected behind the armor suffer no injury from the impact. However, when the projectile hits the armor near a free edge of the armor, separation and/ or delamination of the backing may occur at the free edge, permitting particles of ceramic and of the projectile to escape behind the armor, in which case personnel or equipment behind the armor, but in the path of such particles, may not be adequately protected.

We have discovered that it is possible to back the ceramic plate by means of metal plate, which may be aluminum alloy, which is deformed by and thus absorbs the energy of an impacting projectile. In the case of a hit near a free edge of this composite, it is possible for the metal plate to be momentarily deflected to the degree that particles of the ceramic and the projectile may escape behind the armor. Primarily because of this propensity of metal plates to deflection, in designing caliber .50 armor systems, it was discovered that armor panels with unsupported edges would not perform satisfactorily unless they were ve r y heavy in design. We have further discovered that if the backing plate is provided with a flange 0r lip enclosing the panel edge, the beam strength of the backing material is greatly increased, as well as its resistance to deflection under impact. In accordance with our invention, a flange or lip is provided along all free edges of the backing plate, thereby providing not only increased beam strength, but also enclosing the edges to effectively prevent passage of high velocity particles therethrough or therefrom.

THE DRAWINGS FIG. 1 shows a cross section of our improved ceramic composite armor;

FIG. 2 shows a cross section of our improved ceramic composite armor which has been hit by a projectile centrally of the plate, and

3,592,942 Patented July 13, 1971 As shown in FIGS. 1 and 2, the preferred embodiment comprises a tile 10 of hard ceramic material, which may be high temperature fabricated polycrystalline alumina, silicon carbide or boron carbide. The ceramic tile 10 is backed by an aluminum alloy backing element 12, the preferred alloy being composed of aluminum alloy 2024-T3. To improve its effectiveness, the aluminum alloy backing element 12 is formed at its edge into a flange or lip 14 which extends from the backing element at an angle of substantially adjoining the edge 16 of the ceramic tile 10 and materially stiffening and strengthening the free edge.

The backing element 12 may be bonded to the ceramic tile 10 by means of suitable commercial resin adhesives, for example by an epoxy resin adhesive.

The particular dimensions of the ceramic face plate and the backing element depend upon the specific requirements for the armor panel and the particular materials which are employed in its manufacture. For purposes of illustration merely, the composite armor panel shown in FIGS. 1 and 2 may be three-quarters of an inch in overall thickness, the ceramic face plate 10 being one-half inch thick and the aluminum backing element 12, one-quarter inch thick. When a projectile impacts against the tile or plate 10 as shown in FIG. 2 at 18, the projectile, if it strikes the ceramic face with sufficiently high energy, will shatter and the ceramic plate 10 will similarly shatter. The energy delivered to the aluminum alloy backing 12 by the impact will be dissipated and absorbed. In FIG. 2, the result of the impact of an armor piercing round with the composite ceramic armor panel is shown. While it has not been demonstrated conclusively, it is believed that the mechanics of defeating an armor piercing round with a ceramic armor system are as follows:

During the initial few microseconds after impact, the projectile fractures the ceramic and the ceramic fractures the projectile. When the fracture process has been completed, the aluminum backing material begins to yield, going into a tensile stress condition and continuing to yield until it has been deformed adequately to absorb all the kinetic energy of the fractured ceramic and projectile. The aluminum backing element 12 behind the impact point 18 is deformed into bulge 22. In this procedure, the aluminum backing material and the bulge 22 formed therein have absorbed all the kinetic energy and maintained the ceramic and projectile particles substantially in place.

If an armor panel with unsupported edges is designed to defeat a projectile, such as a caliber .50 armor piercing projectile, within 1.5 inches of an unsupported edge, the matter of deflection becomes important, since transient deflection following impact may permit ceramic and projectile particles to travel in paths behind the backing material. FIG. 3 shows the effect of a projectile impact at 20 against the tile plate 10, the impact point 20 being adjacent an unsupported edge of the armor panel. As previously described, on impact the projectile shatters and the ceramic tile 10 also. The energy transferred from the projectile to the ceramic tile has the immediate effect of deflecting the armor panel rearwardly, a movement which if of large enough extent permits projectile and ceramic particles to move in paths behind the armor panel. The armor panel is greatly stiffened by the lip 14 extending from the backing element 12 whereby the transient deflection, due to the increased beam strength of the backing element, is maintained at a minimum.

Also, energy delivered to the aluminum alloy backing 12 is dissipated and absorbed by deformation of the backing element which may result in a bulge 22 behind the impact point 20, and may deform the lip 14 similarly, whereby the flanged backing element serves effectively to contain the particles of the projectile and ceramic tile formed and energized upon impact. The provision in the design of the lip 14 enclosing the unsupported edges of the ceramic face plate provides the strongest armor panel possible, within any given weight limitations.

We claim:

1. In a composite armor panel having a free edge and capable of providing protection against small arms projectiles and including a high density ceramic face plate, the improvement which strengthens and stifiens the free edge of said panel and prevents passage of high velocity particles in paths behind the panel following impact of a projectile on the face plate near the free edge, said improvement comprising a metal backing plate adhered by a resin adhesive to said face plate, said backing plate having an edge portion at the free edge of the panel which is disposed substantially 90 to form a lip enclosing the adjacent edge of the ceramic plate.

4 2. A composite armor panel as in claim 1 wherein said metal backing plate is aluminium alloy.

3. A composite armor panel as in claim 1 wherein said metal backing plate is aluminum alloy 2024-T3.

5 4. A composite armor plate as in claim 2 wherein said high density ceramic plate is made of a material selected from the group consisting of polycrystalline alumina, sili con carbide and boron carbide.

References Cited UNITED STATES PATENTS DOUGLAS J. DRUMMOND, Primary Examiner US. 01. X.R. 

